As promised, as part of the work I have been doing with the latest version of SCCM Technical Preview, I thought I'd cover one of the new features in the platform - namely, Windows PE Peer Cache.
What is it?
'Windows PE Peer Cache' is a new capability in SCCM which allows a Task Sequence to access content from a local peer on the same subnet instead of downloading content from a Distribution Point.
In a nutshell, there are two components; a Peer Cache Client (a computer configured to obtain content) and a Peer Cache Source (a computer that is configured to share content from a full OS).
Why is it useful?
It minimises the requirement to obtain source data multiple times from a Distribution Point. Content can be obtained once (by the first client to execute the Task Sequence) and then shared to other clients as needed. It also reduces load on the Distribution Point servers.
What types of content are supported by Windows PE Peer Cache?
There is a limitation on the types of content which is supported. Currently it is restricted to:-
- Operating system (OS) images
- Driver packages
- Packages and Programs (When the client continues to run the task sequence in the full operating system, the client gets this content from a peer cache source if the task sequence was originally configured for peer cache when running in Windows PE. )
- Additional boot images
What types of content are NOT supported by Windows PE Peer Cache?
There are two types of content which never transfer using this new technology:-
- Software Updates
What happens if a client cannot obtain content from a Peer Cache Source?
The client will automatically obtain content from a relevant Distribution Point automatically.
How do you configure Windows PE Peer Cache?
The following pre-requisites are required to configure:-
- Client Settings must be amended to enable 'Windows PE Peer Cache' feature
- Cache size on clients must be large enough to accommodate all cached content - more information on amending cache sizes can be found in my other blog post here.
- Task Sequence deployment type must be set to 'Download content locally when needed by task sequence'
- Communication Port 8004 must be open - Used for initial network broadcast
- Content Port 8003 must be open - Used by clients to download content from Peer Cache Source. HTTPS will be preferred, but will default down to HTTP if required. Both methods use the same port.
In addition, when you configure the task sequence use the following task sequence variables as Collection Variables on the collection to which the task sequence is deployed:-
This enables the client to use Windows PE Peer Cache.
When you do not use the default ports configured in the Client Settings (8003 and 8004), you must configure this Variable with a custom value of the network port to use for the initial broadcast.
This flags the content in the task sequence to be retained in the Configuration Manager client cache after the deployment. This is different than using SMSTSPersisContent which only preserves the content for the duration of the task sequence and uses the task sequence cache, not the Configuration Manager client cache.
How can I turn a Peer Cache Client into a Peer Cache Source?
There are three ways this can be done:-
- A peer cache client that cannot find a peer cache source with the content will download it from a distribution point. If the client receives client settings that enable peer cache and the task sequence is configured to preserve the cached content, the client becomes a peer cache source.
- A peer cache client can get content from another peer cache client (a peer cache source). Because the client is configured for peer cache, when it runs a task sequence that is configured to preserve the cached content, the client becomes a peer cache source.
- A client runs a task sequence that includes the optional step, Download Package Content, which is used to prestage the relevant content that is included in the Windows PE Peer Cache task sequence.
Any additional caveats?
Yes. Task Sequences must be started from boot media. If the Task Sequence is started from within the Operating System then Windows PE Peer Cache is not used.
More information on this new feature can be found at the TechNet website here.
Hope this helps.